The present invention relates to a lock mechanism for securing a door kinematics system of an airplane door.
Over the last few years the number of incidents in which unauthorized passengers have tried to get outside a plane during flight and to open a door of the airplane has risen. If such a passenger should succeed in opening a door, this would have catastrophic consequences because the deploying evacuation slide on the airplane could cause it to crash or the sudden drop in cabin pressure could hurl the staff and passengers out of the airplane.
In this respect the necessity exists for a lock mechanism so as to secure doors of the airplane against unauthorized opening.
It is, therefore, an object of the present invention to make a lock mechanism for securing a door kinematics system of an airplane door available, which with a simple design and simple, inexpensive production can safely lock an airplane door and if required, particularly in case of an emergency, can release the locked state of the door.
This object is achieved with a lock mechanism comprising a control unit, an actuator for actuating a locking system and an automatic reset device. The lock mechanism is furthermore designed in such a way that the control unit actuates the actuator as a function of the existence of a predetermined signal in order to bring the locking system into the locked position. When required, especially in case of an emergency, the automatic reset device returns the locking system autonomously into a released state so that the airplane door can be opened from the inside. Furthermore, the automatic reset device ensures that, for example upon failure of an individual component of the lock mechanism, the lock mechanism is also returned into the unlocked state so as to allow actuation of the door kinematics system for opening the door.
Beneficially the lock mechanism comprises a rotatory actuator. The use of a rotatory actuator hereby offers a high level of operational reliability while requiring little space, especially when it comes to locking a door during flight. A brushless DC motor is preferably used as the rotatory actuator. Such a motor is compact, requires only a little space and has a low weight. Furthermore, such motors are largely maintenance-free and exhibit a high level of reliability. Another possibility for a rotatory actuator is the use of a driving mechanism with a solenoid, with which an inexpensive driving mechanism can be made available; however, this rotary actuator has a higher weight and greater space requirement than a DC motor.
In a particularly preferred design, the predetermined signal, as a function of which the control unit actuates the actuator, is a “flight” signal of the airplane. In this way, it can be ensured that the lock mechanism always automatically locks the door kinematics system during flight.
Another preferred possibility for making the predetermined signal available is to equip the system with a switch, for example in the cockpit, wherein the predetermined signal is generated upon actuation of the switch and the lock mechanism locks the door kinematics system. Such a switch can for example also be used for maintenance purposes or for checking the function of the lock mechanism on the ground.
So as to enable a reduction in the input speed of the actuator, the lock mechanism furthermore preferably contains a transmission, especially a planetary gear system.
The automatic reset device preferably contains a spring element, which allows a particularly inexpensive lock mechanism to be made available. In an even more preferred design the automatic reset device comprises at least two spring elements, which each are able individually to reset the locking system from the locked position into the released position. In this way, a redundancy of the reset device is enabled, compensating even for the failure of a spring element, and even greater safety is achieved for cases where the locking system has to be reset in cases of emergency. The spring elements are preferably prestressed by bringing the locking system in the locked position. In this way, the reset device is always automatically transferred into its tensioned state when the door kinematics system becomes locked.
The spring resistance of the spring element is preferably selected in such a way that the spring element is in a position to bring the locking system into the released position from the locking position within just a few seconds.
Furthermore, it is preferred that the rotatory actuator is designed in such a way that it, when switched current-less, also acts as a brake when the locking system is returned from the locked position into the released position. This enables a damped resetting of the locking system.
The locking system beneficially comprises a hook and a brace element with a recess, in which the hook engages in the locked state and thus blocks the door kinematics system. In order to prevent mechanical stress from being applied on the locking system during the locked state, a separate stop element is preferably provided, which establishes a starting and/or ending position without applying stress on the hook itself.
The control unit preferably selects the actuator such that the speed is reduced when approaching the stop in order to achieve gentler stopping.
Pursuant to another preferred design of the present invention, the control unit selects the actuator such that with a suitable signal the locking system is actively pushed in the release direction.
The invented lock mechanism is suitable especially also for retrofitting airplanes that are already being used with appropriate modifications. Since the invented lock mechanism has a very light and compact design, it can generally be installed without difficulty between doorframe segments of the door.
The following is a description of the present invention based on a preferred exemplary design shown in the drawings.